A diesel engine is 20% to 30% more efficient than a gasoline engine but produces more emissions. BlueTec, the new diesel system from Mercedes-Benz, addresses the matter. In order to meet diesel emission regulations in all 50 states, BlueTec uses two catalytic converters and a urea injection system to remove pollutants from the exhaust. The first catalytic converter traps nitrogen oxide and then moves it to the second converter, which turns it into water and nitrogen